Compact light projection system including an anamorphic reflector assembly

ABSTRACT

A compact light projection system. The light projection system includes a light source, an anamorphic reflector assembly, and a correction element that is configured to mitigate aberration. The light source is configured to emit image light. The anamorphic reflector assembly includes a first surface and a second surface. The first surface is configured to reflect the image light toward the second surface which reflects the reflected image light to output it from the anamorphic reflector assembly. And the first surface and the second surface are both curved and non-rotationally symmetric such that the light output from the anamorphic reflector assembly is collimated image light. The collimated image light is optically corrected based in part on mitigation of aberration by the correction element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/886,438, filed Feb. 1, 2018, which is incorporated by reference inits entirety.

BACKGROUND

The present disclosure generally relates to optical collimators, andspecifically relates to a light projection system that includes ananamorphic reflector assembly for artificial reality applications.

Headsets in virtual reality applications typically display image contentvia some form of display. For virtual reality (VR) applications it isdesirable to have a light headset of a small form factor. But, designinga display for such a headset is difficult. In particular, in cases wherethe headset is something akin to a set of eyeglasses. A projectionsystem in the display generates the image light. However, a combinationof space constraints (e.g., very compact), field of view (e.g., wide tofacilitate an immersive VR experience), and an external stop locationtend to greatly limit optical designs for projectors and have limitedconventional headset design.

SUMMARY

A compact light projection system for use in artificial reality systems.The light projection system includes one or more light sources, ananamorphic reflector assembly, and a correction element. The one or morelight sources are configured to emit image light and the correctionelement is configured to mitigate aberration (e.g., chromatic). In someembodiments, the one or more light sources are strip sources. Theanamorphic reflector assembly includes a first surface and a secondsurface. The first surface is configured to reflect the image lighttoward the second surface which reflects the reflected image light tooutput it from the anamorphic reflector assembly. And the first surfaceand the second surface are both curved and non-rotationally symmetricsuch that the light output from the anamorphic reflector assembly iscollimated image light. The collimated image light is opticallycorrected based in part on mitigation of aberration by the correctionelement. In some embodiments, the correction element is configured toreceive the collimated image light from the anamorphic reflectorassembly, and optically correct the collimated image light to formoptically corrected light. In other embodiments, the correction elementis located elsewhere in the light projection system (e.g., between thelight source and the anamorphic reflector assembly).

In some embodiments, the light projection may include a field lens theacts to correct for field curvature, correct for high order fielddependent aberration, correct a chief ray angle, correct for chromaticaberration, or some combination thereof. And in some embodiments, theanamorphic reflector assembly is a monolithic optical element, and thecorrection element may be a Pancharatnam Berry Phase (PBP) lens that isconfigured to correct for at least chromatic aberration. In someembodiments, the PBP lens may also be curved.

The light projection system may be part of a near-eye display (NED) thatis part of an artificial reality system configured to present contentvia the NED to the user.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a light projection system, in accordancewith one or more embodiments.

FIG. 2 is a perspective view of a light projection system that includesa field lens, in accordance with one or more embodiments.

FIG. 3 is a perspective view of a light projection system includingmultiple light sources, in accordance with one or more embodiments.

FIG. 4A is a diagram of a near-eye-display (NED), in accordance with anembodiment.

FIG. 4B is a cross-section of the NED illustrated in FIG. 4A, inaccordance with an embodiment.

FIG. 5 illustrates an isometric view of a waveguide display with a lightprojection system, in accordance with an embodiment.

The figures depict embodiments of the present disclosure for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles, or benefits touted, of the disclosure described herein.

DETAILED DESCRIPTION

System Overview

FIG. 1 is a perspective view of a light projection system 100, inaccordance with one or more embodiments. The light projection system 100provides substantially collimated light to a scanning mirror assembly110 (e.g., of a near-eye display). The light projection system 100includes a light source 120, an optical surface 130, an anamorphicreflector assembly 140, and a correction element 150. In alternativeconfigurations, different and/or additional components may be includedin the light projection system 100. Likewise in alternativeconfigurations, one or more components may be positioned differently inthe light projection system 100.

The light source 120 is one or more strip sources. A strip source is arectangular array of light emitters. A light emitter is a device thatemits light. A light emitter may be, e.g., a light emitting diode (LED),a microLED, a laser diode, some other device that emits light, or somecombination thereof. A strip source may be a 1 dimensional array (e.g.,1×1000 pixels) or a 2 dimensional array (e.g., 10×1000 pixels). In someembodiments, the light source 120 is monochromatic. In otherembodiments, the light source 120 is polychromatic. For example, in someembodiments, a strip source in the light source 120 may includesub-pixels of different colors (e.g., red, green, and blue). The lightsource 120 emits in one or more bands of light. The bands of light mayinclude, e.g., visible light and/or infrared light. In some embodiments,the light source 120 includes one or more microlenses. The one or moremicrolenses are positioned to adjust an orientation of light emitted bythe light source 120, and in particular adjust an orientation of a chiefray (also known as a principal ray) of the light projection system 100.The chief ray crosses an optical axis at the locations of pupils of thelight projection system 100. In some embodiments each light emitter hasa corresponding micro lens. In other embodiments, a single microlens maydirect light from a plurality of light emitters, and in someembodiments, a single microlens may direct light for all of the lightemitters in the light source 120.

The anamorphic reflector assembly 140 collimates the image light. Theanamorphic reflector assembly includes a first reflective surface 160and a second reflective surface 170. The reflective surfaces 160 and 170together not only collimate the image light, but also compress the longdimension of the image light—and thus act as an anamorphic opticalsystem. The first reflective surface 160 and the second reflectivesurface 170 are coated to reflect light in a band emitted by the lightsource 120. In the embodiment shown in FIG. 1, the first reflectivesurface 160 and the second reflective surface 170 are two mirrors thatare separated by an air gap. In alternate embodiments (not shown) thefirst reflective surface 160 and the second reflective surface 170 arecoated surfaces on a monolithic optical element. Additionally, as amonolithic optical element, the anamorphic reflector assembly 140 alsoincludes an optical surface 130. The optical surface 130 may be shapedto correct for aberration. The monolithic optical element may becomposed of, e.g., plastic, glass, or some other material that istransmissive to the image light. In embodiments, where the anamorphicreflector assembly 140 the material of the monolithic optical element isselected such that an index of refraction is within a range of, e.g.,1.4 to 2.8 for visible light, and in embodiments, where the lightemitted by the light source 120 is IR light, the range of indices may behigher.

The first reflective surface 160 and the second reflective surface 170are surfaces that may include, e.g., freeform surface, a Zernikepolynomial surface, a Chebychev polynomial surface, some other form ofparameterized equation that models an asymmetric surface, some otherform of parameterized equation that models a symmetric surface, or somecombination thereof.

The correction element 150 is one or more optical elements that areconfigured to optically correct the collimated image light to formoptically corrected light. The optical correction performed by thecorrection element 150 may be, e.g., to correct for chromaticaberration, correct distortion, correct some other aberration, or somecombination thereof. The correction element 150 as illustrated in FIG. 1is a plurality of optical elements (e.g., a doublet), including at leastone curved lens.

Note that in cases where the anamorphic reflector assembly 140 is amonolithic optical element, substantial dispersion may occur as theimage light travels through the material of the monolithic opticalelement. The dispersion causes chromatic aberration. In alternateembodiments (not shown), the correction element 150 is a PancharatnamBerry Phase (PBP) lens that is configured to correct for at leastchromatic aberration. As an Abbe number of a PBP lens has a reverse signof the monolithic optical element, a PBP lens acts to mitigate chromaticaberration. Moreover, since the Abbe number (e.g., Zeonex E48R has anAbbe number of ˜60) of a PBP lens is ˜one order of magnitude higher thanpotential materials of the monolithic optical element (e.g., a typicaldiffractive has an Abbe number of ˜3), a PBP lens with very littleoptical power can correct color aberration caused by the monolithicoptical element that has a lot of optical power relative to the PBPlens. Additionally, in embodiments, where the color correction element150 is a flat PBP lens, it can actually be placed in other locations inother locations in the light projection system 100. For example, the PBPlens could be placed between the light source 120 and the reflectorassembly 140, such that light from the light source 120 passes throughthe PBP lens prior to being incident on the first reflective surface 160of the reflector assembly 140. Additionally, as a PBP lens may be formedas a flat structure that takes minimal space, relative to, e.g., amulti-element lens (e.g., a doublet). Accordingly, use of a PBP lens asthe correction element 150 may help reduce a form factor of the lightprojection system 100.

In some embodiments where the where the color correction element 150 isa PBP lens, it is curved in at least one dimension. The PBP lens mayhave one or more surfaces that are curved in 1 dimension (e.g.,cylindrical), or the PBP lens may have one or more surfaces that arecurved in 2 dimensions (e.g., spherical, asphericial, freeform, etc.).The PBP is deposited onto a substrate to form the color correctionelement 150. In some embodiments, the substrate is curved prior todeposition of the PBP. Alternatively, the PBP and substrate is curvedafter deposition. Additionally, in some embodiments, the substrate maybe deposited onto an optical surface of a separate optical element, suchthat the color correction element 150 is directly coupled to theseparate optical element (e.g., thereby reducing a number of separateoptical elements in the light projection system 100).

Curvature of the PBP lens can affect its efficiency. The PBP lensincludes a surface that receives light from the reflector assembly 140.The curvature of the PBP lens in the color correction element 150 issuch that an angle of incidence is within some threshold value. Forexample, for any given ray of light that is incident at a point on thesurface, an angle between the given ray and a normal vector at the pointon the surface is at most 3 degrees. By having the curvature of the PBPlens be such that incident light is substantially normal, the PBP lensoperates efficiently. In particular, by having the curvature of the PBPlens be less than some threshold value, it ensures, that minimal changesin magnification occur as a function of distance from an optical centerof the PBP lens.

The light projection system 100 has an external stop 180 that is remotefrom the correction element 150. The external stop 180 is a pupil forthe light projection system 100. In some embodiments, a diameter of theexternal stop 180 may be, e.g., at least 0.5 to 5 mm. A stop distance190 separates the correction element 150 from the external stop 180. InFIG. 1, the scanning mirror assembly 110 is located at the external stop180. However, in alternate embodiments, other components may be placedat the external stop 180 instead of the scanning mirror assembly 110.For example, an in-coupling area of a waveguide or a fold mirror. It isadvantageous to have the stop distance 190 be small, as it, e.g., allowsfor a compact system. The stop distance 190 may range from, e.g., 0 to10 mm. In some embodiments, the stop distance 190 is preferably 4 mm. Incontrast, in conventional light projection systems, rotationallysymmetric optics, large form factor and non-ideal external stop locationmake them impractical for incorporating into a wearable head-mounteddisplay.

FIG. 2 is a perspective view of a light projection system 200 includinga field lens 210, in accordance with one or more embodiments. The lightprojection system 200 is substantially similar to the light projectionsystem 100, except that it includes the field lens 210 and a monolithiccorrection element 220 that is coupled to the first reflective surface160.

The field lens 210 is configured to adjust light emitted from the lightsource 120. In some embodiments, the field lens 210 is configured toadjust light by increasing a narrow axis field of view (i.e., the shortaxis of a strip source), correct a chief ray angle, correct forchromatic aberration, or some combination thereof. The field lens 210includes a first surface 230 and a second surface 240 that is oppositethe first surface 230. The first surface 230 receives light from thelight source 120, and the second surface 240 outputs light after it hasbeen adjusted by the field lens 210. The curvature of the first surface230 and the second surface 240 are selected based in part on theadjustment the field lens 210 applies to the light emitted from thesource 120. The first surface 230 and the second surface 240 may be,e.g., a cylindrically curved surface, a spherical surface, an asphericalsurface, a freeform surface, or some combination thereof.

Additionally, in some embodiments, the field lens 210 may include aplurality of optical elements. In some instances the plurality ofoptical elements may include materials of differing indices ofrefraction (e.g., selected to correct for chromatic aberration). In somecases the plurality of optical elements may be separated by an air gap.The field lens 210 may be composed of glass, plastic, or some othermaterial that is substantially transparent to light from the lightsource 120.

FIG. 3 is a perspective view of a light projection system 300 includingmultiple light sources, in accordance with one or more embodiments. Thelight projection system 300 is substantially similar to the lightprojection system 100, except that it includes a plurality of lightsources and corresponding optical surfaces. In this embodiment, thelight projection system 300 includes a light source 310, a light source320, an optical surface 330, an optical surface 340, an anamorphicreflector assembly 350, and a correction element 360. The light source310 and the light source 320 are substantially similar to the lightsource 120, the optical surface 330 and the optical surface 340 aresubstantially similar to the optical surface 130, the anamorphicreflector assembly 350 is substantially similar to the anamorphicreflector assembly 140, and the correction element 360 is aresubstantially similar to the correction element 150.

In alternative configurations, different and/or additional componentsmay be included in the light projection system 300. For example, in someembodiments, the light projection system 300 may include one or morefield lenses that adjust light emitted from the light sources 310 and320. Likewise, in alternative configurations, some components of thelight projection system 300 may be located in different positions thanthose illustrated in FIG. 3. For example, the correction element 360 maybe positioned elsewhere in the light projection system 300.

The light source projection system 300 has a field of view that spansthe external stop 180. Light emitted from the light source 310corresponds to a first half of the field of view, and is adjusted by theoptical surface 330 and the anamorphic reflector assembly 350 such thatit is collimated. The correction element 360 optically corrects thecollimated image light to form optically corrected light for the firsthalf of the field of view. In FIG. 3, the first half of the field ofview spans a distance from a center of the external stop 180 to a stopboundary 370. Similarly, light emitted from the light source 320corresponds to a second half of the field of view, and is adjusted bythe optical surface 340 and the anamorphic reflector assembly 350 suchthat it is collimated. The correction element 360 optically corrects thecollimated image light to form optically corrected light for the secondhalf of the field of view. In FIG. 3, the second half of the field ofview spans a distance from the center of the external stop 180 to a stopboundary 380.

As the light projection system 300 utilizes multiple light sources thateach emit light that corresponds to a different portion of the field ofview, overall brightness of the light projection system 300 is increasedrelative to, e.g., a single source light projection system.Additionally, in embodiments where a scanning mirror assembly (e.g., thescanning mirror assembly 150) are located at the external stop 180, ascan angle of the scanning mirror assembly is reduced by half.

Note that while the light projection system 300 includes two lightsources 310, 320 and two optical surfaces 330, 340, in alternateembodiments (not shown) the light projection system 300 may includeadditional light sources and corresponding optical surfaces. Forexample, the light projection system 300 may be modified to include athird light source and corresponding optical surface such that eachlight source emits light corresponding to a third of a field of view ofthe modified light projection system.

FIG. 4A is a diagram of a near-eye-display (NED) 400, in accordance withan embodiment. In some embodiments, the NED 400 may be referred to as ahead-mounted display (HMD). The NED 400 presents media to a user.Examples of media presented by the NED 400 include one or more images,video, audio, or some combination thereof. In some embodiments, audio ispresented via an external device (e.g., speakers and/or headphones) thatreceives audio information from the NED 400, a console (not shown), orboth, and presents audio data based on the audio information. The NED400 is generally configured to operate as an artificial reality NED.

The NED 400 shown in FIG. 1 includes a frame 405 and a display 410. Theframe 405 is coupled to one or more optical elements which togetherdisplay media to users. In some embodiments, the frame 405 may representa frame of eye-wear glasses. The display 410 is configured for users tosee the content presented by the NED 400. As discussed below inconjunction with FIGS. 4B and 5, the display 410 includes at least onedisplay assembly (not shown) for directing one or more image light to aneye of the user. The display assembly includes a waveguide display thatincludes one of the light projections systems described above withreference to FIGS. 1-3.

FIG. 4B is a cross-section 450 of the NED 400 illustrated in FIG. 4A, inaccordance with an embodiment. The display 410 includes at least onedisplay assembly 460. An exit pupil 470 is a location where an eye 480is positioned in an eyebox region when the user wears the NED 400. Forpurposes of illustration, FIG. 4B shows the cross section 450 associatedwith a single eye 480 and a single display assembly 460, but inalternative embodiments not shown, another display assembly which isseparate from the display assembly 460 shown in FIG. 4B, provides imagelight to an eyebox located at an exit pupil of another eye of the user.

The display assembly 460, as illustrated below in FIG. 4B, is configuredto direct the image light to an eyebox located at an exit pupil 470 ofthe eye 480. The display assembly 460 may be composed of one or morematerials (e.g., plastic, glass, etc.) with one or more refractiveindices that effectively minimize the weight and widen a field of view(hereinafter abbreviated as ‘FOV’) of the NED 400.

In some configurations, the NED 400 includes one or more opticalelements between the display assembly 460 and the eye 480. The opticalelements may act to, e.g., correct aberrations in image light emittedfrom the display assembly 460, magnify image light emitted from thedisplay assembly 460, some other optical adjustment of image lightemitted from the display assembly 460, or some combination thereof. Theexample for optical elements may include an aperture, a Fresnel lens, aconvex lens, a concave lens, a filter, or any other suitable opticalelement that affects image light.

FIG. 5 illustrates an isometric view of a waveguide display 500 with asource assembly 510, in accordance with an embodiment. In someembodiments, the waveguide display 500 is a component (e.g., displayassembly 460) of the NED 400. In alternate embodiments, the waveguidedisplay 500 is part of some other NED, or other system that directsdisplay image light to a particular location.

The waveguide display 500 includes a source assembly 510, an outputwaveguide 520, and a controller 530. For purposes of illustration, FIG.5 shows the waveguide display 500 associated with a single eye 480, butin some embodiments, another waveguide display separate (or partiallyseparate) from the waveguide display 500, provides image light toanother eye of the user. In a partially separate system, one or morecomponents may be shared between waveguide displays for each eye.

The source assembly 510 generates light in accordance with displayinstructions from the controller 530. The source assembly 510 includes alight projection system, and optionally includes a scanning mirrorassembly. The light projection system may be, e.g., the light projectionsystem 100, the light projection system 200, or the light projectionsystem 300. The scanning mirror assembly may be, e.g., the scanningmirror assembly 150. The light projection system emits light inaccordance with display instructions received from the controller 530.The source assembly 510 generates and outputs image light 540 to acoupling element 550 of the output waveguide 320.

The output waveguide 520 is an optical waveguide that outputs imagelight 560 to the eye 480. The output waveguide 520 receives the imagelight 540 at the coupling element 550, and expands the image light inone or more dimensions and outputs the expanded image light using thedecoupling elements 570 and 580 as the image light 560. The couplingelement 550 and the decoupling elements 570 and 580 may be, e.g., adiffraction grating, a holographic grating, one or more cascadedreflectors, one or more prismatic surface elements, an array ofholographic reflectors, and some combination thereof. An orientation andposition of the image light exiting from the output waveguide 520 iscontrolled by changing an orientation and position of the image light540 entering the coupling element 550.

The output waveguide 520 may be composed of one or more materials thatfacilitate total internal reflection of the image light received fromthe source assembly 510. The output waveguide 520 may be composed ofe.g., silicon, plastic, glass, or polymers, or some combination thereof.The output waveguide 520 has a relatively small form factor. Forexample, the output waveguide 520 may be approximately 50 mm wide alongX-dimension, 30 mm long along Y-dimension and 0.5-1 mm thick alongZ-dimension.

The controller 530 determines display instructions for the sourceassembly 510. Display instructions are instructions to render one ormore images. In some embodiments, display instructions may simply be animage file (e.g., bitmap). The display instructions may be receivedfrom, e.g., a console of an artificial reality system. Displayinstructions are instructions used by the source assembly 510 togenerate image light. The display instructions may include, e.g., a typeof a source of image light (e.g. monochromatic, polychromatic), ascanning rate, an orientation of a scanning apparatus, sourcewavelength, pulse rate, pulse amplitude, beam type (continuous orpulsed), other parameter(s) that affect the emitted light, or somecombination thereof. The controller 530 includes a combination ofhardware, software, and/or firmware not shown here so as not to obscureother aspects of the disclosure.

Additional Configuration Information

The foregoing description of the embodiments of the disclosure has beenpresented for the purpose of illustration; it is not intended to beexhaustive or to limit the disclosure to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the abovedisclosure.

Some portions of this description describe the embodiments of thedisclosure in terms of algorithms and symbolic representations ofoperations on information. These algorithmic descriptions andrepresentations are commonly used by those skilled in the dataprocessing arts to convey the substance of their work effectively toothers skilled in the art. These operations, while describedfunctionally, computationally, or logically, are understood to beimplemented by computer programs or equivalent electrical circuits,microcode, or the like. Furthermore, it has also proven convenient attimes, to refer to these arrangements of operations as modules, withoutloss of generality. The described operations and their associatedmodules may be embodied in software, firmware, hardware, or anycombinations thereof.

Any of the steps, operations, or processes described herein may beperformed or implemented with one or more hardware or software modules,alone or in combination with other devices. In one embodiment, asoftware module is implemented with a computer program productcomprising a computer-readable medium containing computer program code,which can be executed by a computer processor for performing any or allof the steps, operations, or processes described.

Embodiments of the disclosure may also relate to an apparatus forperforming the operations herein. This apparatus may be speciallyconstructed for the required purposes, and/or it may comprise ageneral-purpose computing device selectively activated or reconfiguredby a computer program stored in the computer. Such a computer programmay be stored in a non-transitory, tangible computer readable storagemedium, or any type of media suitable for storing electronicinstructions, which may be coupled to a computer system bus.Furthermore, any computing systems referred to in the specification mayinclude a single processor or may be architectures employing multipleprocessor designs for increased computing capability.

Embodiments of the disclosure may also relate to a product that isproduced by a computing process described herein. Such a product maycomprise information resulting from a computing process, where theinformation is stored on a non-transitory, tangible computer readablestorage medium and may include any embodiment of a computer programproduct or other data combination described herein.

Finally, the language used in the specification has been principallyselected for readability and instructional purposes, and it may not havebeen selected to delineate or circumscribe the inventive subject matter.It is therefore intended that the scope of the disclosure be limited notby this detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsis intended to be illustrative, but not limiting, of the scope of thedisclosure, which is set forth in the following claims.

What is claimed is:
 1. A system comprising: an anamorphic reflectorassembly including a first reflective surface and a second reflectivesurface of a monolithic optical element, the first reflective surfaceconfigured to reflect image light toward the second reflective surfacewhich reflects the reflected image light to output it from theanamorphic reflector assembly, and the first reflective surface and thesecond reflective surface are both curved and non-rotationally symmetricsuch that the light output from the anamorphic reflector assembly iscollimated image light; and a correction element configured to mitigatechromatic aberration based in part on the correction element having anAbbe number that is opposite in sign to an Abbe number of the monolithicoptical element, and wherein the collimated image light is opticallycorrected based in part on mitigation of chromatic aberration by thecorrection element.
 2. The system of claim 1, wherein the correctionelement is a Pancharatnam Berry Phase (PBP) liquid crystal lens.
 3. Thesystem of claim 2, wherein the PBP liquid crystal lens receives imagelight from the anamorphic reflector assembly.
 4. The system of claim 2,wherein the PBP liquid crystal lens includes at least one curved surfacecurved in 1-dimension.
 5. The system of claim 2, wherein the PBP liquidcrystal lens includes at least one curved surface curved in2-dimensions.
 6. The system of claim 2, wherein the anamorphic reflectorassembly receives the image light from the PBP liquid crystal lens. 7.The system of claim 2, wherein the PBP liquid crystal lens is flat. 8.The system of claim 2, wherein the PBP liquid crystal lens includes afirst surface and a second surface, and the PBP liquid crystal lens iscurved such that for any given ray of the optically corrected light thatis incident at a point on the first surface, an angle between the givenray and a normal vector at the point on the first surface is at most 3degrees.
 9. The system of claim 1, wherein the Abbe number of thecorrection element is an order of magnitude larger than the Abbe numberof the monolithic optical element.
 10. The system of claim 1, whereinthe image light is a visible band of light.
 11. The system of claim 1,wherein the image light is emitted by a strip source.
 12. The system ofclaim 11, wherein the strip source is selected from a group consistingof: a linear array of micro-light emitting diodes, and a linear array ofvertical cavity emitting lasers.
 13. The system of claim 1, wherein thecorrection element receives image light from the anamorphic reflectorassembly, and the system has an external stop at a stop distance fromthe correction element.
 14. The system of claim 13, further comprising ascanning mirror configured to scan the optically corrected light in atleast one dimension, the scanning mirror placed at a location of theexternal stop.
 15. The system of claim 13, wherein the stop distance isat most 10 mm.
 16. The system of claim 1, further comprising a fieldlens positioned between the anamorphic reflector assembly and a lightsource that emits the image light, such that the image light from thelight source passes through the field lens prior to entering theanamorphic reflector assembly, and the field lens is configured toperform at least one of: increase a field of view, correct a chief rayangle, and correct chromatic aberration.
 17. The system of claim 1,wherein the image light is emitted by a light source that includes afirst strip source and a second strip source.
 18. The system of claim17, wherein the system has a field of view that spans an external stop,and light emitted from the first strip source corresponds to a firstportion of the field of view, and light emitted from the second stripsource corresponds to a second portion of the field of view that isdifferent than the first portion.
 19. The system of claim 18, whereinthe field of view is divided into a first half and a second half, andthe first portion corresponds to the first half and the second portioncorresponds to the second half.
 20. The system of claim 1, wherein thesystem is part of a waveguide display that is part of a near-eye device.